EP0684021A1 - Stent with mutually linked wires - Google Patents

Abstract

The stent has a tubular reticulation of at least two bands of filaments joined at intersections. Each separate band (11) consists of at least two parallel filaments (13) joined at points and interfitting at intersections (12). The filaments have a rectangular cross-section. The filaments are joined by weld-points (16), before or after the intersection parts. The filaments are made of a memory material such as metal or plastics. The reticulation on the exterior surface has a surface producing higher frictional values. <IMAGE>

Description

The invention relates to a stent for splinting and / or for keeping a hollow organ open, with a tubular and self-expandable network consisting of filaments, which is stretched in the axial direction in the collapsed state of the lumen and shortened in the axial direction in the expanded state of the lumen, and that from at least two Bands is built up.

Such a stent is described in European application EP 94 106 490.9.

The transluminal application of stents for splinting or permanent stretching of stenoses or other forms of lumen restriction of hollow organs is particularly advantageous for patients with increased surgical risk. Surgical and diagnostic interventions can be supplemented with the help of interventional radiology and with the help of various visual diagnostic options or, in the best case, become superfluous. The transluminal implantation of stents makes it possible to keep a vascular lumen or a hollow organ permanently open.

The stent described in the abovementioned EP patent application is constructed from bands which are rectangular in cross section and are fixed to one another at crossover points of the stent. In the collapsed state, the known stent has a smaller diameter than a self-expanding stent made of round filaments, and the stent, which has a rectangular cross section, can be produced from a smaller number of bands. The connection of the bands at the crossing points is achieved in that the bands are completely covered at the crossing points. The bands can move with respect to one another within the coated layer. Depending on the material selected for the sheath, a restoring force can be increased from the collapsed state of the stent to the expanded state. The ligaments lie against one another at their crossing points over their metallic surfaces and the intersecting ligaments are entirely covered with plastic, so that a fixed joint is formed at the crossing point.

The invention has for its object a self-expanding To further develop the stent of the type mentioned at the outset in such a way that the filaments lie as evenly as possible on the inner wall of a hollow organ, that the restoring forces of the stent can be expanded via the crossing points, and that the stent is used safely and stably by improving the articulation of the crossing points becomes.

This object is achieved in that each individual band consists of at least two mutually parallel, point-to-point filaments which interlock at intersection areas.

Splitting the tape into at least two parallel, point-to-point filaments that mesh with one another at the crossing points allows the stent to be produced with crossing regions that no longer need to be coated to produce a joint at the crossing point. As a result, the crossing point is converted into a crossing area, the punctual forces of the crossing point being distributed over the crossing area in a manner that is gentle on the tissue. In addition, a relaxation of the restoring force due to fatigue of the coating material at the cross points is no longer possible, because the joint formed at the cross points is no longer held together by a coating, but is formed by the interlocking mesh of the bands consisting of at least two filaments.

In a preferred embodiment of the invention, the cross-sectional shape of the filaments is rectangular. This embodiment has the advantage that the stent is smaller Can have a diameter, such as a self-expanding stent made of round filaments. The stent according to the invention thus lies flat on the inner wall of a hollow organ and is gentle on the tissue, and the filaments do not press linearly on the adjacent tissue. The position of the individual filament can be determined optically over the entire length of the stent. If a steel flat strip is used for the production of the stent according to the invention, which is considerably wider than it is high, the stent is very thin in the stretched state and can be inserted and placed safely through the lumen of the hollow organ via very thin insertion instruments. Furthermore, the stent according to the invention in this embodiment exhibits great variability in diameter, length and expansion strength with great longitudinal flexibility. This is achieved in that, in the case of a flat strip, the differently directed force components are also of different sizes, in contrast to a round wire in which the force components resulting from it are always of the same size. In this embodiment, the stent according to the invention can adapt better to the most varied courses of the hollow organs. A flat contact with the inner wall of the hollow organ to be stretched can also reduce the pressure load and any excessive intimal hyperplasia or granulation formation in the area of the stent ends.

In a further embodiment of the invention, the filaments end in parallel at the free ends of the stent and are connected to one another. This has the advantage that the free ends of the stent cannot have any sharp corners or edges that could injure the tissue or that could also contribute to problematic removal of the stent. This fixation of the ends ensures that the lumen has only a slightly enlarged diameter at the free ends, but ensures sufficient fixation of the stent.

In a development of this embodiment, the free ends of the stent are rounded. This measure has the advantage that the stent also lies gently against the tissue in the end region, and possible injury or irritation of the loaded tissue through the end region of the stent can be avoided.

The stent according to the invention can also have filaments which are at least partially provided with a sheath. This measure has the advantage that a possible desired coating or surface can also be applied to the filaments, as a result of which an improved biocompatibility of the stent can be achieved or a special tissue-protecting effect can be achieved. In addition to a rubber-elastic coating or a coating made of plastic, hydrophilic or antithrombogenic coatings can also be provided on the tapes. A hydrophilic coating enables improved flow values at the extended locations in the hollow organ.

In another embodiment, the filaments of each band are connected to one another at points in front of and behind the crossing regions. This measure has the advantage that the intersection areas are kept mechanically stable and defined, so that in the collapsed as well as in the expanded state, the restoring forces at the intersection points are advantageous be distributed and reproducible. This arrangement achieves a stable mechanical arrangement.

The point connections can be made by welding spots or the like. This has the advantage that proven welding techniques can be used for the production of the stent according to the invention, which enable an effective and inexpensive as well as a safe and reliable connection of the filaments assembled into a band.

In a further embodiment of the invention, the filaments are made from memory material. The use of e.g. a memory alloy, e.g. Nitinol wire or tape, for example, allows the stent to be guided to the appropriate vascular sites via a known introducer and expanded in situ, thereby assuming a material-stored final shape.

It is also possible to produce the stent from plastic or metal. Depending on the requirements, the biocompatibility of the stent and / or the tissue-protecting effect can thereby be improved.

In a further embodiment of the invention, the net has a surface on the outer surface that generates increased friction values. This measure has the advantage that the stent finds a secure, immovable fit in the hollow organ after insertion into the hollow organ.

Furthermore, the entire stent can be plastic or drug-coated if necessary. This results in embodiments where the sheathing covers the spaces between the bands.

Fig. 1

einen erfindungsgemäßen Stentabschnitt in ausgedehntem Zustand mit Freiräumen und einem Netz, das aus acht Bändern besteht;

Fig. 2

einen Abschnitt eines erfindungsgemäßen Stents mit sechs Bändern;

Fig. 3

eine vergrößerte Darstellung eines Kreuzungsbereiches im ausgedehnten Zustand;

Fig. 4

eine expandierte Darstellung des Kreuzungsbereiches im kollabierten Zustand;

Fig. 5

einen Endabschnitt eines Stents im Bereich eines freien Endes;

Fig. 6

einen Abschnitt eines aus zwei Filamenten bestehenden einzelnen Bandes in gerader Erstreckung;

Fig. 7

einen Querschnitt gemäß VII-VII der Fig. 6;

Fig. 8

einen Abschnitt eines einzelnen Bandes mit zwei runden Filamenten;

Fig. 9

einen Endabschnitt eines Stents im Bereich eines freien Endes.

Further advantages result from the description and the attached drawing. Likewise, according to the invention, the features mentioned above and those which have been elaborated further can be used individually or in any combination with one another. The mentioned embodiments are not to be understood as an exhaustive list, but rather have an exemplary character. The invention is illustrated in the drawing and is explained using exemplary embodiments. It shows:

Fig. 1

a stent section according to the invention in an expanded state with free spaces and a network consisting of eight bands;

Fig. 2

a section of a stent according to the invention with six bands;

Fig. 3

an enlarged view of an intersection area in the expanded state;

Fig. 4

an expanded representation of the intersection area in the collapsed state;

Fig. 5

an end portion of a stent in the region of a free end;

Fig. 6

a section of a single band consisting of two filaments in a straight extension;

Fig. 7

a cross section according to VII-VII of Fig. 6;

Fig. 8

a section of a single ribbon with two round filaments;

Fig. 9

an end section of a stent in the region of a free end.

The individual figures of the drawing show the subject according to the invention in a highly schematic manner and are not to be understood to scale. The objects of the individual figures are shown greatly enlarged so that their structure can be shown better.

1 shows a stent section 10 of a stent consisting of eight bands 11 in a largely expanded state of the lumen. The helical bands 11 delimit a cylindrical volume and form a braided network that defines a substantially cylindrical hollow body. Each band 11 consists of two adjacent filaments 13 running parallel to one another and the bands 11 cross at intersection areas 12, the filaments 13 intermeshing in terms of braiding. The network runs around a central axis of symmetry 14 in a longitudinal direction. The network formed from the bands 11 has free spaces 15, the size of which depends on how many bands 11 were used to create the network, and whether the network is in the collapsed state of the lumen or in the expanded state of the lumen. The filaments 13 each belonging to a band 11 are held together by means of connections 16. The connections 16 are arranged behind and in front of the intersection areas 12 in such a way that a stable intersection area 12 is ensured which can absorb large restoring forces in a movable manner.

2 shows a stent section 20 according to the invention of a stent consisting of six bands 21. Each band 21 consists of two filaments 23 running parallel to one another, which engage in the filaments 23 of another band 21 in crossover areas 22. The filaments 23 designed according to FIG. 2 of six ribbons 21 define a cylindrical volume which runs around a central axis 24 and is enveloped by the braided network. 2 is shown in the expanded state of the lumen. In the case of the stent according to FIG. 2 consisting of six bands 21, free spaces 25 have been created which can have a different size and shape compared to those of the exemplary embodiment according to FIG. 1.

FIG. 3 shows an enlarged stent section 30 of a stent consisting of four bands 31 in the expanded state of the lumen. The ribbons 31 are each made of two filaments 33 which overlap one another at intersection areas 32. 3 provides a cylindrical lumen that runs symmetrically about a central axis 34. The network has free spaces 35, the size and shape of which, even in the expanded state of the lumen, depends on the size and shape of the free spaces, which consists of the stent constructed with eight bands 11 according to FIG. 1 and the stent having six bands 21 according to FIG. 2 can be formed. The respective filaments 36 of each band 31 are held together by means of connections 36, the connections 36 being arranged in front of and behind the crossing areas 32 in such a way that a stable crossing area 32 is created. In the expanded state of the lumen, the intersection area 32 has between the two interlocking bands 31 a crossing angle α.

4 shows a section of an intersection area 42 of a stent according to the invention in the collapsed state of the lumen. In this state, the stent is axially stretched, with the lumen collapsing. The two bands 41, each consisting of two filaments 43, overlap in the intersection area 42. Connections 46, which can also have weld seam properties, are produced in front of and behind the intersection area. In the collapsed state, the bands 41 crossing in the intersection area 42 have an intersection angle β which is significantly smaller than the intersection angle in the expanded state of the lumen (angle α of FIG. 3) and the free spaces 45 of the network are correspondingly reduced. In the collapsed state of the lumen, an intersection gap 47 is formed by the intermeshing filaments 43 of the two bands 41, which forms a cuboid surface. In contrast to the free spaces 45, which generally have a smaller area in the collapsed state than in the expanded state of the lumen, the crossing gaps 47 can also have larger open areas in the collapsed than in the expanded state. In this way, it is possible to distribute the crossing area 42 over an even larger area in the collapsed state than in the expanded state of the lumen, as a result of which greater storage of restoration energy in the crossing area 42 is achieved and a stable crossing area 42 is created. The formation of an intersection gap 47 in the collapsed state of the lumen causes the filaments 43 belonging to a band 41 to be split out, which, in contrast to the expanded state, where the parallel filaments 43 of a band 41 largely lie in a common one Level, spread apart slightly, with the restoring forces in the filaments 43 being spring-loaded on the basis of the connections 46.

5 shows a stent section 50 in the region of the free end 58. The network running symmetrically about an axis 54 is composed of six bands 51 and each band 51 consists of two filaments 53. The free end 58 of the stent begins immediately after the crossing regions 52 The crossing bands 51 define free spaces 55. Connections 56 are provided directly after the crossing regions 52, which finally hold the two filaments 53 of a band 51 parallel to one another, also at the free end 58 of the stent. At the free end 58, the filaments 53 have rounded portions 59, which ensure a gentle contact with the tissue of the hollow organ.

FIG. 6 shows a section of a band 61 made of two parallel filaments 63, each with a rectangular cross section. The filaments 63 are held together by means of a welding point or connection.

Fig. 7 shows a cross section through the segment of Fig. 6 according to section VII-VII. The band 71 shown in cross section consists of two respectively rectangular filaments 73 and each filament 73 has a core 74 and a sheathing 75, the sheathing being able to be made of tissue-protecting material.

Finally, FIG. 8 shows an embodiment of the band 81, in which the band 81 consists of wire-shaped filaments 83 with a round cross section.

9 shows another exemplary embodiment of a stent section 90 in the region of the free end 98. The network running symmetrically about an axis 94 consists of eight bands 91 and each band 91 is made up of two filaments 93. The free end 98 of the stent begins after the crossing areas 92 and the intersecting bands 91 define free spaces 95. Connections 96 are provided directly in front of the crossing regions 92, which hold the two filaments 93 of a band 91 parallel to one another and also at the free end 98 of the stent . At the free end 98, the filaments 93 have final roundings 99, which ensure gentle contact with the tissue of the hollow organ.

A self-expanding stent for hollow organs is presented for splinting and / or for keeping a hollow organ open. The stent consists of bands 11 which span a tubular and self-expanding network. In a collapsed state of the lumen, the network is stretched in the axial direction and in an extended state of the lumen in the axial direction, and the network is constructed from at least two bands 11. According to the invention, each individual band 11 is produced from at least two filaments 13 running parallel to one another, which are connected to one another at points and which interlock at cross regions 12.

Claims (9)

Stent for splinting and / or for keeping a hollow organ open, with a tubular and self-expandable network consisting of bands (11; 21; 31; 41; 51; 61; 71; 81), which in the collapsed state of the lumen in the axial direction (14; 24; 34; 54) stretched and shortened in the extended state of the lumen in the axial direction (14; 24; 34; 54) and which is constructed from at least two bands (11; 21; 31; 41; 51; 61; 71; 81), characterized in that each individual band (11; 21; 31; 41; 51; 61; 71; 81) consists of at least two filaments (13; 23; 33; 43; 53; 63; 73; 83) which are connected to one another at certain points ) which interlock at intersection areas (12; 22; 32; 42; 52). Stent according to claim 1, characterized in that the cross-sectional shape of the filaments (13; 23; 33; 43; 53; 63; 73; 83) is rectangular. Stent according to claim 1 or 2, characterized in that the filaments (53) end at free ends (58) of the stent (50) and run parallel to one another. Stent according to one of the preceding claims, characterized in that the filaments (73) at least partially have a core provided with a sheath (75) (74). Stent according to one of the preceding claims, characterized in that the filaments (13; 23; 33; 43; 53; 63; 73; 83) of each band (11; 21; 31; 41; 51; 61; 71; 81) before and behind the intersection areas (12; 22; 32; 42; 52) are connected to one another at points. Stent according to one of the preceding claims, characterized in that the filaments (13; 23; 33; 43; 53; 63; 73; 83) are connected to one another via welding spots (16; 26; 36; 46; 56; 66) or the like . Stent according to one of the preceding claims, characterized in that the filaments (13; 23; 33; 43; 53; 63; 73; 83) are made of a memory material. Stent according to one of the preceding claims, characterized in that the filaments (13; 23; 33; 43; 53; 63; 73; 83) consist of metal or plastic. Stent according to one of the preceding claims, characterized in that the mesh has a surface on the outer surface which generates increased friction values.

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